Is there any way (in preferences, for instance) to keep palette windows from docking and/or merging with each other? I like to keep them separated, but they seem to stick (or nestle) together without conscious prompting on my part. It drives me crazy!

Basically, no. That's the way the interface works in all the Adobe applications I'm familiar with. You can float individual panels, however, but if you move them so they begin to touch or overlap other panels, the blue highlighting means that they could be docked or merged.

I find that it takes a couple of steps to ensure -- no ifs, ands or buts -- that palettes/panels I want to hang out on their own stay out on their own:

1) Open the panel I want to hang out on its own from the Window pull-down menu. Make a mental note to see if the nested panel group is free-floating or pops out of the side dock. Place my cursor on the tab for the panel I want to separate and click-drag it out onto the desktop. Close the rest of the nested panel group, then move the panel I separated where I want it to be on the desktop.

2) After completing Step 1 above, if I want to keep it in my side dock, again place my cursor in the panel tab and drag it to the blank area at the bottom of the side dock. Done correctly, I should see a separate label/button for the now-independent panel in the side dock.

3) Repeat as necessary for all panels you want to separate from their respective, nested groups.

4) Go to the Window>Workspace>New Workspace... menu command. Make sure the Panel Locations check box is checked and Give it a name -- in my case, I use my first name so in all my Adobe apps they're named Randy's. Then click the OK button.

From there, it's a done deal. Whenever you choose your Workspace, your panels should be where you want them to be. If they should accidentally merge, all you need to do is select the Reset [Your Workspace Name] button in the Control Panel or in the Window>Workspace sub-menu command to get them back the way you want them.